Area Forecast Discussion
Issued by NWS Portland, OR
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Issued by NWS Portland, OR
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-- Discussion containing changed information from previous version are highlighted. --548 FXUS66 KPQR 110924 AFDPQR Area Forecast Discussion National Weather Service Portland OR 224 AM PDT Tue Jun 11 2024 .SYNOPSIS...-- Changed Discussion --High pressure will shift eastward as a weak front pushes through the region today. This may lead to drizzle or light rain along the coast this morning, while inland locations remain dry. Onshore flow will keep things cool, and clearing skies tonight will lead to much cooler Wednesday morning lows. High pressure brings dry and warm conditions Wednesday and Thursday. Friday through early next week, troughing enters the region, resulting in increased precipitation chances and cooler temperatures.-- End Changed Discussion --&& .SHORT TERM...-- Changed Discussion --Today through Thursday...A high pressure ridge aloft will push eastward this morning as an upper level trough approaches British Columbia. Satellite imagery as of 1 AM PDT depicts the associated surface low around 49N/132W, with a cold front draped southward along 128W. This weak front is progressing toward the Pacific Northwest, which is beginning to deepen the marine layer along the coast. The front will push inland around 8-11 AM today, which may result in some morning drizzle or light rain along the coast (15-30% chance). It doesn`t appear that this front will be robust enough to lead to any precipitation within the Willamette Valley, but do expect increased broken/overcast cloud cover inland in this morning. An exception would be the Eugene area, where the front may be slow enough to arrive such that the first half of the day has plenty of sunshine before the front arrives early this afternoon. Given the increased cloud cover today, expect afternoon high temps for interior valleys to be a few degrees cooler than yesterday. Forecast highs are in the mid 70s for interior valleys and upper 50s/low 60s along the coast. While most locations will experience northwesterly winds with gusts up to 20 mph this afternoon, westerly winds in the Central Columbia River Gorge could gust up to 40 mph. Tonight, high pressure will re-build as the weak front dies off. As a result, expect a decrease in cloud cover and lighter winds. It`ll be a pretty cool night for June, with tomorrow morning lows in the mid to upper 40s for lowlands and upper 30s for higher terrain. Though we`ll start off Wednesday pretty cool, the air mass will warm up later in the day with sunny skies so tomorrow afternoon highs should end up seasonable. High pressure will persist through Thursday, leading to another cool night Wednesday night, but probably not quite as cold as Tuesday night. As the air mass continues to warm Thursday, it appears likely Thursday afternoon will be a few degrees warmer than mid-June normals. Based on NBM guidance, it appears there is a 40-50% chance of the Portland Metro Area reaching 80 deg F Thursday afternoon, while chances for the same in Eugene are closer to 10-20%. -Alviz/Weagle-- End Changed Discussion --&& .LONG TERM...-- Changed Discussion --Friday through Monday...The upper ridge begins to shift east of the forecast area on Friday as another trough near the Gulf of Alaska dips southward toward the Pacific Northwest. This will lead to a cooling trend and return of precipitation chances. It currently looks like a weak front will brush the coast and northern part of our CWA, so Friday`s PoPs are pretty low (15-40% chance) and confined to the coast, Coast Range, and southwest Washington. Saturday, most ensemble members agree on troughing entering the region with below-normal 500 mb heights. In this scenario, we would see increasing chances for widespread precipitation and below average temperatures. For now, the NBM`s 25-60% chance of PoPs across northwest Oregon and southwest Washington at the end of the week look reasonable. Sunday to Monday, the majority of ensemble members (>85%) continue to show broad troughing over the Pacific Northwest, maintaining a generally cool and potentially wet start to next week. -Alviz-- End Changed Discussion --&& .AVIATION...-- Changed Discussion --At 2 am, VFR with scattered high clouds across the region. But, do have widespread IFR to lower end MVFR along the coast as marine stratus blankets the coastal areas. Increasing onshore flow today, as front approaches. This will push stratus deep into the coast range/Willapa Hills valleys, and into parts of the interior by 12Z to 13Z. Do not think entire Willamette Valley will cloud over, but will have areas of MVFR against the Cascades foothills. As morning progresses, marine layer near surface will deepen, and as such, will see increasing marine stratus spread across much of the interior, but will likely be lower VFR (3000 to 4000 ft clouds). Even coast will likely lift to VFR this afternoon. Once the front passes, will see winds turn more northwesterly, with CIGS gradually breaking up towards evening. With the uptick of onshore flow, expect breezy west winds in the mid/eastern Columbia Gorge, and over higher terrain in Cascades. PDX AND APPROACHES...At 2 am, still VFR with scattered high clouds. Should see patchy MVFR to north and east of PDX from 12Z to 16Z, possible backbuilding enough to form a BKN-OVC CIGS after 14Z. As front draws closer, will see increasing clouds by mid to late morning, with CIGS mainly 3000 to 4000 ft. CIGS will slowly break part late in the afternoon into the evening. /Rockey-- End Changed Discussion --&& .MARINE...-- Changed Discussion --Not a lot of change. Even though weak front will push across the region, high pressure will quickly restrengthen over the offshore waters behind the front this afternoon through tonight. As such, northerly winds will pick up again later today, but mainly tonight and remain gusty at times through Wed evening. Have Small Craft Advisory on the waters, spreading from north to south as the front moves across region and pressure gradient tightens. Seas mainly 5 to 7 ft, but will see seas up around 10 to 12 ft for a time later today into early Wed am as fetch of large swell moves from northeast Pac into the north Washington waters. High pressure will maintain northerly gradients through Thu, though the north winds will be bit less, generally 10 to 20 kt, with strongest in afternoons/evenings. Seas stay in the 5 to 6 ft range. Next front will arrive later Fri, with flip back to W or SW winds of 10 to 15 kt for late Fri into early Sun. /Rockey-- End Changed Discussion --&& .PQR WATCHES/WARNINGS/ADVISORIES...-- Changed Discussion --OR...None. WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Wednesday for PZZ210. Small Craft Advisory from 11 AM this morning to 11 PM PDT Thursday for PZZ251-252-272. Small Craft Advisory from 5 PM this afternoon to 11 PM PDT Thursday for PZZ253-273. Small Craft Advisory from 8 AM this morning to 11 PM PDT Thursday for PZZ271.-- End Changed Discussion --&& $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland